From the Help -> Changelog
(Notice: this list is not compiled by me)

v1.5

Fixed the bug with index out of bounds when reading news.
It is now possible to "lock" windows so they cannot be moved with the mouse. It is a setting under the tab menus.
The keyboard backspace bell sound that was reintroduced in 1.41 (mainly for Vista) should be gone again.
Text that goes into the map window will now be sent through the trigger functions as well.
The "move all frames into view" should now work for frames that are either outside of the view at the top of the desktop or the left side. (It failed to set those correctly before.)
You can now also change transparency settings for map and battle windows.
The "useTrigger" parameter when creating triggers should now work as it should.
The /trigtest command (internal for the client) will produce a little more output now indicating which triggers that give a match to the argument string.
Rooms that does not support map, should no longer spam into the generic window when the map window is closed.
A new partyframe has been added. It shows the status of your group. You can change the way statusbar texts are displayed by right-clicking at the top of the frame. You can also change alpha settings from that menu. Right-clicking on the different party "slots" when they are occupied by players gives you a menu with handy party commands if you are leader.
An out of formation (OOF) party frame has been added. This frame will show party members that are out of formation in the party.
It is now possible to use global variables through the commandline (commandparser) with the format "@variable".
Keybindings should now send their commands through the commandparser and not directly to the server. This way global variables can be used inside keybinding commands.
If you left-click on an occupied slot in the party frame you will "select" that player and put the name of the player into a global variable called "partyTarget". To tell the person you have clicked on you can use: "tell @partyTarget your message". With this variable you can assign keys or macros to perform certain actions against the selected party member. For example you could set F1 to heal selected member and when you see their health bar go down, you click on their slot and press F1.
Two more global variables are available. "selectedTarget" which will be set whenever you click on stuff in the main text window for example, and "latestTarget" which will be set whenever you click somewhere both in the party frame and in other windows.
You can now see your own location on the realm map. If you right click on the map you can also select "move to YOU" which will center the map over your location in the world. You will also see the location of all your group members.
It is now possible to bind the command "/commandline focus" to any key for setting the focus to the last used commandline.
A new trigger menu has been added in the settings menu. You can now select if triggers should only be triggered in visible windows. You can also toggle the debug mode on triggers. If debug is on, it will send debug information to the "trigger_debug" channel. (Enable this channel in a window if you wish to see the debug output).
The commandline backlog functionality now includes any unfinished commands that are written when the history up arrow is pressed. (The unfinished command will be put at the end of the backlog as if it has been executed like a normal command).
The tab menu that popups when right-clicking on window tabs should now work with left-click + control key as well.
The character face images used in the party frames and the realm map window should now be fetched from the web server based on the player name. If no image can be found for a particular player, a default image based on race and gender will be used instead.
All triggers will now be checked against incoming text. Before only one trigger was executed and others that should have triggered on the same text were skipped.
"Auto-logging" has been added. Each tab in each window can be configured to be autologging. It will then start logging automatically when the client is started. The logfile is created with the following name format: "yyyymmdd-tabname.txt".
A new "status monitor" has been added. It can be opened from the settings menu. It will show your personal status, ep, sp, hp and your current target.
Words shorter than 3 characters are no longer triggered with the tab autocomplete feature in the commandline.
A space character is inserted after tab completed word now.
All tab completed words will be printed in lowercase to the commandline.
When clicking the close button on windows the focus will be returned to the last used commandline.
When opening windows from the bottom menu bar the focus will be given to the last used commandline.
Tab autocomplete will now search through your commandline history for words as well.
You can now change the default ansi colors in each tab through the tab-menu.